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nilfs2: enhance btree node keys check

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syzbot reported a warning on nilfs_btree_assign:
WARNING: fs/nilfs2/btree.c:2302 at nilfs_btree_assign+0x983/0xbe0 fs/nilfs2/btree.c:2302,

Analysis found that a corrupted file has the following btree layout:
Level2(key/ptr): [ 256/15 ]
Level1(key/ptr): [ 0/8, 1/9, 0/10, 3/11, 4/12, 5/13, 6/14,
                   139637976727559/16, 0/17 ]

The test truncated the file to 2 bytes, which partially zeroes the first
block and adds the file to the dirty list. When the segment constructor
writes it and assigns a new blocknr for the index block, it searches the
btree with key=0 and min level=2, and apparently returns -ENOENT.

Therefore, we should perform more checks on the btree nodes and return
early.

[ryusuke: split long lines in btree.c to satisfy checkpatch and
 improved the error message format for clarity]

Reported-by: syzbot+158be45e4d99232e1900@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=158be45e4d99232e1900
Signed-off-by: Wang Jianjian <wangjianjian3@huawei.com>
Fixes: 17c76b0104 ("nilfs2: B-tree based block mapping")
Cc: stable+noautosel@kernel.org # Warning suppression primarily
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Signed-off-by: Viacheslav Dubeyko <slava@dubeyko.com>
This commit is contained in:
Wang Jianjian 2026-08-10 23:20:52 +09:00 committed by Viacheslav Dubeyko
parent 6b38b82be4
commit d7d54599a1
1 changed files with 16 additions and 3 deletions
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19
fs/nilfs2/btree.c
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@ -341,7 +341,8 @@ static int nilfs_btree_node_broken(const struct nilfs_btree_node *node,
sector_t blocknr)
{
int level, flags, nchildren;
int ret = 0;
__u64 key, prev_key;
int i;
level = nilfs_btree_node_get_level(node);
flags = nilfs_btree_node_get_flags(node);
@ -356,9 +357,21 @@ static int nilfs_btree_node_broken(const struct nilfs_btree_node *node,
"bad btree node (ino=%llu, blocknr=%llu): level = %d, flags = 0x%x, nchildren = %d",
inode->i_ino, (unsigned long long)blocknr, level,
flags, nchildren);
ret = 1;
return 1;
}
return ret;
for (i = 1, prev_key = nilfs_btree_node_get_key(node, 0);
i < nchildren; i++, prev_key = key) {
key = nilfs_btree_node_get_key(node, i);
if (unlikely(key <= prev_key)) {
nilfs_crit(inode->i_sb,
"bad btree node (ino=%llu, blocknr=%llu): unsorted keys at index %d (%llu) and %d (%llu)",
inode->i_ino, (unsigned long long)blocknr,
i - 1, prev_key, i, key);
return 1;
}
}
return 0;
}
/**